1. Technical Field of Invention
The invention relates to a construction machine that includes a control unit that controls charging and discharging of an electric storage device.
2. Description of Background Art
In the related art, a construction machine such as a hybrid construction machine or an electric construction machine that includes an electric storage device and a control unit that controls charging and discharging of the electric storage device in order to suppress the deterioration of the electric storage device is known (for example, Japanese Unexamined Patent Publication No. 2010-193630, hereinafter it is called patent literature 1.).
In the construction machine disclosed in patent literature 1, the charge and discharge current of the electric storage device is limited according to the magnitude of internal resistance of the electric storage device based on information indicating an outside air temperature and the magnitude of an internal resistance of the electric storage device based on information (integrated use time) indicating deterioration of the electric storage device (see claims 1 and 4 and paragraphs [0025] to [0028]).
As in the technique disclosed in patent literature 1, providing a limiting value for the charge and discharge current of the electric storage device according to the magnitude of the internal resistance of the electric storage device is essential to suppress the deterioration of the electric storage device and secure the safety thereof.
However, the magnitude of the internal resistance of the electric storage device also changes according to an operation state of the construction machine. Therefore, as in the construction machine disclosed in patent literature 1, even when the charge and discharge current is controlled according to the magnitude of the internal resistance based on the outside air temperature and deterioration of the electric storage device, the charge and discharge current of the electric storage device may be limited too excessively in an operation state where the internal resistance of the electric storage device is maintained to a low value.
In this case, the ability of the electric storage device is unnecessarily suppressed due to the limited charge and discharge current, and excessive performance (specification) is required for the electric storage device to exercise sufficient ability in such a situation.
As a result, the cost of the electric storage device increases, and the size of the electric storage device may increase. An increase in the size of the electric storage device makes compression on the layout of equipment of the construction machine.